The present disclosure relates to a control system for an internal combustion engine equipped with an electric supercharger.
An exhaust gas recirculation (EGR) system, for a vehicle equipped with an internal combustion engine, reduces nitrogen oxide emissions by recirculating exhaust gas into intake gas for environmental protection. In a diesel engine equipped with an EGR system, particulate matter (PM) and wet soot (WS) that accumulate as deposit on parts that form the internal combustion engine may cause degradation in the performance of such parts. Various cleaning methods have been proposed to remove deposit that has accumulated on parts that form the internal combustion engine.
Japanese Patent Application Publication 2008-057489 mentions a diesel engine that has an intake passage and an exhaust passage provided with an EGR cooler and an intercooler, and removes particulate matter accumulated on the EGR cooler. In the diesel engine of the Publication, a cleaning passage is formed by controlling the operation of valves disposed in the intake and exhaust passages, and cleaning to remove particulate matter accumulated on the EGR cooler is performed after a stop.
Japanese Patent Application Publication 2012-102670 mentions an EGR system that closes an EGR passage in response to an engine stop advance signal to stop the flow of exhaust gas from the EGR passage into an intake passage just before the engine stops. Then, the rotation speed of a turbine shaft is increased thereby to increase the blowing force of the compressor. This EGR system permits not only removing deposit accumulated on the compressor wheel and the intercooler by the blowing force, but also removing deposit accumulated on the compressor wheel by the centrifugal force.
In a vehicle having an internal combustion engine which is equipped with both a turbocharger and an electric supercharger, the electric supercharger is driven to supplement supercharging when supercharging provided only by the turbocharger is insufficient. In such internal combustion engines equipped with an electric supercharger, if the EGR passage is connected to the intake passage at a position that is upstream of the electric supercharger, there is a fear that particulate matter in emission may be accumulated on the compressor wheel of the electric supercharger, a bearing, and a sealing member of the electric motor. Since accumulation of deposit on the electric supercharger causes degradation in supercharging performance and an increase of sliding resistance, there is a need for deposit to be removed.
The present invention provides a control system of an internal combustion engine that removes deposit that is accumulated on an electric supercharger of the internal combustion engine.